Method and apparatus for supplying liquefied gas



Feb. 7, 1961 J. H. BECKMAN ET AL 2,970,452

METHOD AND APPARATUS FOR SUPPLYING LIQUEFIED GAS Filed April 1, 1959 2Sheets-Sheet 1 f INVENTORS JOHN H. BECKMAN EUGENE H. KEMP A TTORAIEY i Ia Feb. 7, 1961 J. H. BECKMAN ETAL 2,970,452

METHOD AND APPARATUS FOR SUPPLYING LIQUEIFIED GAS 2 Sheets-Sheet 2 FiledApril 1, 1959 INVENTORS JOHN H. BECKMAN EUGENE H. KEMP WZ/MJM M,

ATTORNEY United States Patent C) METHOD AND APPARATUS FOR SUPPLYINGLIQUEFIED GAS Filed Apr. 1, 1959, Ser. No. 803,466

14 Claims. (Cl. 62-51) This invention relates to an improved method ofand apparatus for supplying low-boiling liquefied gas, and moreparticularly to a portable double-walled container for carryingliquefied gas and discharging fluid therefrom when the container is inany position or under any gravity condition, as for example in aircraftor underseas.

Oxygen, nitrogen and air, for example, are widely used to providebreathing atmospheres or for pressurizing fuel systems and controlmechanisms. These gases are conveniently stored in the liquefied form toreduce the total storage volume and vessel weight required to supply agiven volume of gas. Many such systems must be portable, as for examplewhere oxygen is to be supplied for high altitude and deep-sea breathingpurposes. This need for portable, light-weight equipment emphasizes thepotential advantages of liquid storage as contrasted from pressurizedgas storage containers. Low boiling liquefied gas containers are usuallyconstructed with double walls, the space between the inner and outerwalls being provided to insulate the liquid in the inner vessel from theatmospheric heat. This is necessary because such liquefied gases arestored at very low temperatures, e.g. l83 C. for liquid oxygen, andwithouthigh quality insulation the liquid would vaporize very quickly.

Most prior art liquefied gas storage containers deliver the desiredliquid outlet flow only when properly positioned and under the influenceof gravity. When these containers are inverted or when gravity iseliminated, as would be encountered in space flight, the liquid deliveryeither becomes sporadic or ceases completely. Conventional pressurebuilding circuits in which the liquid phase of the container isconnected to the gas phase through a vaporizer could not be used topressurize the liquid in the prior art containers for this type ofservice since these circuits rely on gravity as the pressure drivingforce. Also, the gas phase in these previously proposed containers hasthev disadvantage of being in direct contact with the liquid phase. Whena pressure-building circuit is used, a portion of the vaporized liquidis returned to the gas phase. Hence, when liquid air, for example, isstored therein, a portion of the oxygen will be condensed from the gasphase to achieve equilibrium within the container. This phenomenon willresult in the gas phase always being nitrogen-rich and the liquid phasebeing oxygen-rich with respect to air. Since the container may beoperated in various positions and delivery may occur from either gasphase or liquid phase, the desired composition of the output gas wouldnot be obtained at any moment. This is a serious problem when the storedfluid is used to supply breathing atmospheres to divers or crew membersin aircraft, since for optimum functioning the human body requiresoxygen and nitrogen in a relatively narrow concentration range.

One prior art method which attempts to maintain liquefied gas'flow froma storage container in all positions or under zero-gravity conditionsand which could also be used for liquid air breathing supplies, involvespositioning a flexible bladder inside the storage vessel. The bladder isinflated or collapsed with a gas having a lower boiling point than thestored liquid in order to pressurize the liquid. The main disadvantagewith this system is the requirement of a separate pressure source toinflate or collapse the bladder and thus permit the application orsuflicient pressure to the liquid for forcing such liquid out of thestorage container.

Another previously proposed method of solving this diflicult problem isto incorporate a separate energy source, such as a heating coil, withinthe storage container. Energy can be added in large amounts to vaporizeadditional liquid within the container and thus provide sufficientpressure to force out the liquid. A separate source of energy wouldinvolve an intricate, heavy and costly system. Also, such an arrangementhas the additional critical disadvantage of unsuitability for use withliquid air for breathing purposes since the heat energy input wouldcause a composition change by vaporizing primarily nitrogen.

A principal object of the invention is to provide an improved liquefiedgas storage container capable of dispensing any desired quantity ofliquid from any container position and under any gravity condition.

Another object is to provide an improved liquefied gas storage containerhaving the additional characteristics of lightweight and minimum heatinleak.

Still another object is to provide a method for dispensing any desiredquantity of liquefied gas from a storage container when such containeris in any position and exposed to any gravity condition.

These and other objects and advantages of the invention will becomeapparent from the following description and the accompanying drawings inwhich:

Fig. 1 is a schematic view, mainly in vertical cross section of anexemplary double-walled cylindrical container construction embodying theprinciples of the invention;

Fig. 2 is a schematic view, mainly in vertical crosssection of the lowerportion of an alternate doublewalled container;

Fig. 3 is a schematic view, mainly in vertical crosssection of the topportion of an alternate double-walled container;

Fig. 4 is a view of a longitudinal cross-section of an exemplarydouble-walled cylindrical container embodying another form of theinvention; and

Fig. 5 is a view of a horizontal cross-section taken along the line 5-5of Fig. 4.

In the drawings similar elements in the several figures are designatedby similar reference characters.

In accordance with one embodiment of the present invention, a portablecontainer is provided for storing and dispensing from any containerposition a pressurized liquefied gas having a boiling point below 233 K.The container includes an inner vessel for storing a body of thepressurized liquefied gas, an outer shell enclosing and separating theinner vessel from the atmosphere, and an insulating space under a vacuumpressure between the inner vessel and the outer shell. A piston istransversely positioned across the cross-sectional area of the innervessel so as to substantially fill such area. The piston is alsoarranged and constructed to slidably move in a direction parallel to thelongitudinal axis of the container so as to separate the liquid and gasphases at all levels of the liquid in the inner vessel. Means areprovided for sealing the outer periphery of the slidable piston againstthe inner wall of the inner vessel, and preferably such means constitutea concentrically positioned flexible cylindrical film having one endleak-tightly and circumferentially attached to the inner wall oftheirrier vessel. The other end of the cylindrical film is leaktightlyand circumferentially attached to the outer periphery of the piston. Thepiston also serves as a thermal barrier between the stored liquid andgas phases preventing the gas from rec-ondensing into the liquid, thusmain-v taining a substantially constant composition in the stored liquidand the product gas resulting therefrom. The liquid phase and the pistonare maintained under a slight artificial gravity pressure at allcontainer positions and gravity conditions, by at least one compressiblespring transversely positioned across the inner vessel. The spring islongitudinally located between the upper end of the inner vessel and thetop side of the slidable piston. This combination of interactingelements permits the use of a pressure building circuit even underzero-gravity conditions.

The term vacuum as used hereinafter is intended to refer to the vacuumpressure in the insulating space between the inner vessel and outershell of the portable container of this invention. The term applies tosubatmospheric pressure conditions not substantially greater than 1,000microns of mercury, and preferably below 100 microns of mercuryabsolute.

In a preferred embodiment of the novel portable container, theinsulating space contains an opacified insulating jacket, which is manytimes as efficient as the conventional powder-in-vacuum or highlypolished reflective surfaces heretofore used in double-walled liquefiedgas containers. The use of opacified insulation permits the fabricationof a liquefied gas container having a much narrower insulating space fora given rate of heat inleak, and consequently a smaller and lighter unitfor a given liquid storage capacity. Alternatively, opacified insulationpermits an increased liquid storage capacity for a given weight, ascompared with a container insulated by conventional materials.

The term opacified insulation as used herein refers to a two-componentinsulating system comprising a low heat conductive, radiation-permeablematerial and a radiant heat impervious material which is capable ofreducing the passage of infrared radiation rays without significantlyincreasing the thermal conductivity of the insulating system. Also, theterm radiant heat barrier as used herein refers to radiation opaque orradiant heat energy impervious materials which reduce the penetration ofinfrared heat rays through the insulating system either by radiant heatreflection, radiant heat absorption or both. As defined, opacifiedinsulation includes a mixture of finely divided low-conductive particleswhich substantially impede heat inleak by-conduction and yield to heatpassage by radiation, and finely divided radiant heat impervious bodieshaving a relatively high thermal conductivity. As more fully describedand claimed in copending U.S. Serial No. 580,897, filed April 26, 1956in the name of L. C. Matsch and A. W. Francis, the low conductiveparticles may be selected from the group consisting of silica, perlite,alumina, magnesia and carbon black, and the radiant heat imperviousbodies are preferably either aluminum or copper, although copper paintpigments, alumina paint pigments, magnesium oxide, zinc oxide, ironoxide, titanium dioxide, copper coated mica flakes, carbon black, andgraphite either alone or in combination with each other would givesatisfactory results. Also, these bodies usually in the form of flakesor powder, preferably constitute between 1% and 80% of the total weightof the insulation.

The opacified insulation may also take the form of the combination of alow heat conductive material and a multiplicity of spacedradiation-impervious barriers. As more fully described and claimed incopending US. Serial No. 597,947, filed July 16, 1956 in the name of L.C. Matsch, the low heat conductive material may be the previously listedpowderous materials or alternatively a fiber insulation which may beproduced in sheet form. Examples of the latter include a fila e y glassmillimeter.

terial such as glass wool and fiber glass, preferably having fiberdiameters of less than about 50 microns. Also such fibrous materialspreferably have a fiber orientation substantially perpendicular to thedirection of heat flow across the insulation space. The spacedradiation-impervious barriers may comprise either a metal, metal oxide,or metal coated material, such as aluminum coated plastic film, or otherradiation reflective or radiation adsorptive material or a suitablecombination thereof. Radiation reflective materials comprising thinmetal foils are particularly suited in the practice of the present invention, for example, reflective sheets of aluminum foil having athickness between about 0.2 millimeter and 0.002 Other radiationreflective materials which are susceptible of use in the practice of theinvention are tin, silver, gold, copper, cadmium or other metals. Whenfiber sheets are used as the low-conductive material, they mayadditionally serve as a support means for relatively fragile radiationimpervious sheets. For example, an aluminum foil-fiber sheet insulationmay be spirally wrapped around the inner liquefied gas holding vesselwith one end of the insulation wrapping in contact with the innervessel, and the other end nearest the outer shell, or in actual contacttherewith.

It would normally be concluded by one skilled in the art that theaforedescribed opacified insulation could not be economlcally used inportable liquefied gas containers because of the relatively heavy natureof such insulation. For example, a 50%50% by weight mixture of silicapowder with finely divided copper flakes has a bulk density of about 12lbs. per cubic ft. However, it has been found that opacified insulationpreferably in combination with lightweight aluminum or aluminum alloyconstruction provides an improved liquified gas portable container whichis substantially lighter than heretofore used containers having the samestorage volume and the same insulating efiiciency. This remark. ableresult is attainable in part because the opacified insulatlons used inthis invention have a relatively high insulating efliciency at vacuumspoorer in quality than those required for vacuum-polished metal surfaceinsulation. Because of this characteristic, aluminum, which is known toproduce porous welds, can be used instead of relatively heavierstainless steel or copper which can produce relatively leak-proof metaljoints.

In addition the present novel container is also substantially lighter inweight and requires substantially less fluid storage volume than priorart containers storing compressed gases and supplying the same totalvolume of gas; For example, a container having a liquid storage volumeequivalent to cu. ft. gas capacity built in accordance with thepreferred form of the present invention using aluminum or aluminum alloymaterial for both the inner vessel and outer casing weighs about 29 lbs.empty. This container has an outside diameter of about 7 /4 inches andan overall length of about 29 inches. The container provides about thesame amount of gas as two compressed gas cylinders each of about thesame physical size and each weighing about 34 lbs. empty, the cylindersbeing of a type commonly used in underwater breathv ing equipment.

The thermal insulating effectiveness of opacified insulation versusstraight vacuum plus polished surfaces (no powder insulation) can becompared by using the example of to l-square foot metal plates spaced'Vs inch apart. When straight vacuum insulation was used, the insidesurfaces of the plates were polished to an emissivity of 0.04. The outerplate was a room temperature (70 F.) and the inner plate was at liquidoxygen temperature (-297 F.). Under 50 microns pressure between theplates, an opacified insulation in this space consisting of 50%50% byweight mixture of silica powder and finely divided copper metal flakeshad a heat transmission of about 1.85 B.t.u./hr. In order for straightvacuum insul ation to have a comparable eflectiveness, the pressure Iinvention for reevacuation of the insulating jacket.

games would have to be less than 0.01 micron. Under similar pressureconditions (50 microns) straight vacuum plus polished surfaces had aconsiderably higher heat transmission of about 43 B.t.u./hr. It can thusbe seen that by using opacified insulation a highly efiicient insulatingsystem may be provided in aluminum liquefied gas portable containerseven though the space between the inner vessel and the outer casing ismaintained at a relatively poor vacuum because of the relatively porousnature of the aluminum-containing joints. While a preferred embodimentof this invention includes the above-described opacified insulation asone of several interacting elements, it is to be understood that analternate embodiment of the present portable container may utilizestraight vacuum-polished surface insulation.

Even though the previously described preferred opacilied insulation ismore effective than straight vacuum insulation at higher internalpressures (poorer vacuum), its effective thermal insulation life isextended. if the pressure can be maintained at or below a desired level.A gas removing material such as an adsorbent, either in powder or pelletform, may be used in the insulation space to remove by adsorption thegas entering through the porous aluminum-containing joints. This is anextremely important feature since no provision is made in the relativelysmall portable container of the present The adsorptive capacity ofsuitable adsorbents, such as natural and synthetic zeolites, silica geland activated charcoal, generally rises with increased pressure.Therefore these adsorbents are more effective for removal of insulationjacket air leakage when opacified insulation is used than when straightvacuum is employed because of the higher vacuum space pressure involved.Furthermore, these adsorbents generally have higher adsorptivecapacities at relatively lower temperatures. Consequently they arepreferably mounted adjacent to the cold outer side of the inner vesselwall. Alternatively, the adsorbent may be randomly mixed in theopacified insulation. In particular, crystalline zeolitic molecularsieves having pores of at least about Angstrom units in size, asdisclosed in U.S. Patent No. 2,900,800, issued in the name of P. E.Loveday. are preferred as the adsorbent since they have extremely highadsorptive capacity at the temperature and pressure conditions existingin the insulating jacket and are chemically inert toward any gases whichmight leak into the insulating jacket. Such zeolites may be eithernatural or synthetic. This novel combination of opacified insulal ionand adsorbent thus facilitates construction of a liquefied gas portablecontainer which is lighter in 'weight and has a longer effective lifethan previously proposed containers. Such an adsorbent is alsousedadvantageously in combination with straight vacuumpolished surfaceinsulation.

Referring now more specifically to Fig. 1, the portable liquefied gascontainer generally indicated at includes a liquid holding inner vessel11 which is illustrated as cylindrical in form although other shapessuch as the spherical form would also be suitable. The preferred shapeis primarily determined by the intended use of the container. Forexample, a cylindrically shaped container is preferred for underwaterdiving, because a cylinder is most conveniently attached to the diversback. The inner vessel 11 is completely surrounded and separated fromthe atmosphere by outer casing 12, both containers being preferablyfabricated from aluminum alloy in order to take advantage of itslightweight characteristic. The low density of aluminum especiallyallows a relatively thick outer casing to be used which has moreresistance .to handling abuse than would a relatively thin casing ofequivalent weight fabricated from denser material.

Space 13 under a vacuum separates the outer wall of the inner vessel 11from the inner wall of the outer casing 12, and is preferably filledwith the previously described opacified insulation 14. The preferredform of the opacified insulation used with this invention comprises lowheat conductive material such as glass wool or fiber glass having fiberdiametersof less than about 50 microns, and a multiplicity of spacedradiation-impervious barriers, such as aluminum foil having a thicknessbetween about 0.2 mm. and 0.002 mm. This layered insulation isconveniently assembled around cylindrical inner vessels and tends tohold the inner vessel in spaced relation to the outer shell.Alternatively, the opacified insulation 14 may be a mixture of finelydivided low conductive particles and radiant heat impervious bodieshaving a relatively high thermal conductivity. For example, a 50%-50% byweight mixture of finely dividedsilica powder having particle sizesbelow about microns, and copper flakes smaller than about 50 micronswith a flake thickness less than about 0.5 micron gives best results,although opacified insulation mixtures having larger sizeparticles havebeen tested with excellent re sults. It has been found that the powdertype opacified insulations are particularly suitable for sphericalcontainers because such insulation may be easily poured in the space 13between the inner vessel 11 and the outer casing 12.

Blister or chamber 15 secured to and in heat exchange relation with thebottom section of inner vessel 11 holds a gas-removing material 16 andpreferably an adsorbent such as the previously described synthetic ornatural zeolite to remove gas and vapors from the insulating jacket 14.Adsorbent material 16 communicates with the opacified insulating jacket14 through passages 17 in the walls of chamber 15, the adsorbentmaterial for example being retained in chamber 15 by glass cloth sheets18 extending across the passages and held against the chamber walls byplates 19. It is to be understood that glass cloth sheets 18 do notinterfere with vapor and gas communication between the opacifiedinsulating jacket 14 and adsorbent material 16 although they servetoretain the latter.

The inner vessel 11 is supported and stabilized against all relativemovement (both vertical and lateral) by a suitable support system whichmay, for example, comprise upper suspension member 20 and the layeredinsulation jacket 14 acting in combination. Element 20 is preferablyformed from material such as stainless steel, having the properties ofrelatively high compression and shear strengths, low thermalconductivity, and retention of such properties at temperatures fromabout 1.91 c. to 127 c.

An alternate form of the support system which is especially advantageouswhen opacified powder insulation is used comprises the combination ofupper suspension member 20 and hollow lower support member 20a. The lastmentioned member is also preferably formed from low thermal conductivitymaterial having relatively high compression and shear strengths, such asphenol-formaldehyde resin reinforced with fabric or paper. Lower member20:: may either be mounted in continuous compression or it may befixedly mounted against the inside wall of the outer casing 12 andpositioned so as to slidably and telescopically engage the lower portionof the inner vessel outer wall 11.

The liquid phase zone 21 of the inner vessel 11 is separated from thegas phase zone 22 by piston 23 which is preferably annularly andconcentrically positioned around member 24 extending in a longitudinaldirection from one end to the other end of such inner vessel. Piston 23is also preferably slidably mounted on elongated and longitudinallyaligned member 24 so as to move in a direction parallel to thelongitudinal axis aa of the container, and substantially fill the crosssectional area of inner vessel 11. Member 24 is preferably constructedof a low thermal conductivity material such as organic plastics orstainless steel, and serves to guide the mcvemeutcf piston 23 and, thusprevent amoeba "7 any tipping thereof which might interfere with properoperation. The center section of longitudinal member 24 is solid, andthe extremities thereof are hollowed to provide upper and lower endeductor tube sections 63 and 64, respectively.

The surface of piston 23 sliding on longitudinal member 24 is preferablysealed by sliding seal 24a which may be constructed oftrifluorochloroethylene polymers, tetrafluoroethylene polymers, orpolyethylene terephthalate resin. These materials have been found to beable to withstand temperatures as low as those of liquid oxygen (-l83C.) and liquid nitrogen (-l96 C.) without becoming brittle. Piston 23 ispreferably constructed of a low thermal conductive material such as theaforementioned organic polymers or stainless steel. This is because theheat transfer across the piston must be minimized to decrease boiling inthe liquid phase 21 and condensation in the gas phase 22.

In order to completely separate the liquid and gas phases 21 and 22respectively and thus prevent leakage of liquid around the piston intothe gas phase, it is necessary to seal the outer periphery of theslidable piston 23 against the inner wall of the inner vessel. This ispreferably accomplished through the provision of fiexible film 25 whichis cylindrically shaped and positioned in the annular space between thepiston periphery and the vessel inner wall. One end 26 of thecylindrical film is leak-tightly and circumferentially attached to theouter periphery of piston 23, and the other film end 27 is leak-tightlyand circumferentially attached to the inner wall of the inner vessel.Flexible film 25 is preferably of sufficient length so that it foldsback on itself along circumference 28, and as piston 23 moves up anddown the film furis or unfurls. Film 25 is preferably composed ofpolyethylene terephthalate resin or trifiuorochloroethylene polymersince these materials retain their flexibility at low temperatures, aspreviously discussed. Since the pressure drop across film 25 is onlyabout 1 p.s.i at the most, its thicknessis governed mainly by theflexibility required; thicknesses of about 0.0005 to 0.003 inch aresuitable. Alternatively, a ring-type sliding seal formed from a suitableplastic or metal may be provided instead of flexible film 25.

The liquid phase 21 and piston 23 are maintained under a slightartificial gravity pressure at all container positions and gravityconditions by a pair of compressible springs 29 and 30 separated bymovable ring 31. The springs are longitudinally located between theupper end ofthe inner vessel 11 and the top side of the slidable piston23. A single spring instead of lower and upper springs 29 and 30respectively, could alternatively be provided, but the double springarrangement is preferred from the standpoint of stability. It will beappreciated that a relatively long spring assembly is needed to applypressure to piston 23 as it moves along the full longitudinal length ofthe inner vessel 11. If a single long spring were used, it might tend tobuckle instead of evenly compressing as the piston moves upwardly in thecontainer.

The top surface of upper spring 30 abuts against spring retainer 32having raised center capped section 33 covering the open upper end ofeductor tube section 63. The upper end of spring retainer capped section33 is received in the lower end of inner vessel hollow upper suspensionmember 20, the latter being leak tightly sealed to the edges of anopening in the top header of such inner vessel. The top surface ofcapped section 33 abuts the lower end of relatively small back-up spring34, and the upper end of such spring is retained in center cavitysection 34a of collar 35. The collar member 35 is leaktightly sealed tothe walls of an opening in the elongated upper end 36 of outer casing12.

Rod pointer 37 is secured at one end to spring retainer 32 by suit-ablemeans such as flexible prongs 37a,

and extends in a longitudinal direction through the center section ofback-up spring 34 into center cavity section 34a of collar 35. The upperend of rod pointer 37 extends through a hole in the top of collar 35,and is contained in a recessed central part 39 of sight cap 40 which isleak-tightly secured to the walls of the collar hole. Sight cap 40.isconstructed of transparent material, such as plastic or glass. Theassembly is provided with sufficient clearance between the rod pointer37 and the surrounding elements for free longitudinal movement of suchpointer. The position of piston 23 coincides with the liquid level inthe inner vessel 11, controls the compression'in springs 29 and 30, andthus determines in combination with back-up spring 34, the position ofspring retainer 32 and rod pointer 37. This novel combination providesan improved liquid level gage by calibration of the. pointer positionwith respect to the liquid level in inner vessel 11, the upper end ofrod pointer being observable through transparent cap 40. Alternatively,if an indicating device remote from the container is required, rodpointer 37 may for example be mechanically connected by linkage 70 tovariable resistor 71 in electrical indicating circuit 72, changes inliquid level being observed on meter 73.

The container 10 is filled with liquefied gas by introducing such liquidthrough filling valve 41, conduit 42 and communicating conduit 43 whichextends through insulation jacket 14 and connects with the lower end ofinner vessel 11. Prior tofilling, the combination vent and pressurebuildup valve 44 is placed in the vent position, connecting conduit 45with vent port 46 and closing off conduit 47 on the opposite side ofvalve 44. When liquid filling is commenced, the pressure of the incomingliquid and resulting vapor forces piston 23 upward to a position abovethe orifices 50 in the top eductor tube 63. This allows the gas formedby the liquid vaporizing on the relatively warm walls of the innervvessel 11 to be vented through top orifices 50 back into top eductortube 63 for discharge through hollow upper suspension member 20, collarcavity section 34a, and communicating transverse passageway 51 inadapter 52 which is leaktightly thread connected to collar 35. Thelast-mentioned passageway 51 connects with conduit 45 so that theevaporation gas formed during liquid filling is passed therethrough tocombination vent and pressure buildup valve 44 for venting through port46 to the atmosphere. When the inner vessel is completely-filled withliquid, the velocity of the gas venting through the top orifices 50 willcarry entrained liquid with it, so that when the operator observesliquid being discharged through vent port 46, he will be notified thatthe container is full. After filling is complete, filling valve 41 isclosed and combination vent and pressure buildup valve 44 is placed inthe buildup position, connecting conduit 45 with conduit 47 and closingoff vent port 46.

In a preferred embodiment of the present invention, means are providedfor building gas pressure in the gas phase 22 of inner vessel 11, so asto facilitate the discharge of liquid from such vessel at any desiredrate. The pressure building circuit includes conduit 53 and branchconduit 53a. Branch conduit 53a contains vaporizer 54, pressure closingvalve 55, and relief valve 56 communicating with the downstream side ofpressure closing valve 55. One end of conduit 47 also connects with thedownstream side of pressure closing valve 55, the other end joining withcombination vent and pressure buildup valve 44, as previously described.

Gas pressure is built up in the gas phase zone 22 in the followingmanner: Springs 29 and 3t) exert a downward force on piston 23 whichtransmits the force to the liquefied gas liquid phase 21 causing liquidto enter orifices 57 in the lower eductor tube 64. This liquid flowsconsecutively through communicating conduit 58, threeway valve 59,conduit 53, and into branch conduit 53a. The withdraw liquid then passesthrough vaporizer 54 which is preferably heated by the atmosphere,although 9 other sources of heat, such as steam, warmed air, or water,would also be suitable. The resulting gas is'discharged from vaporizer54 and flows consecutively through pressure closing valve 55, conduit47, combination vent and pressure buildup valve 44, conduit 45,passageway 51 in adapter 52, hollow upper suspension member 20, andfinally through the annular space 60 between member 20 and springretainer 32 into the gas phase zone 22 of inner vessel 11. When the gaspressure in zone 22 has reached the desired level, e.g. 120 p.s.i.g.,pressure closing valve 55 closes and no additional gas enters. If thepressure in gas phase zone 22 becomes excessive, relief valve 56 willopen. The preferred combination or spring compression and gas pressurein zone 22 maintains piston 23 at the liquid level between liquid phasezone 21 and zone 22, and thus keeps the stored liquid under continuouscompressive pressure. This pressure not only forces the liquid out ofthe container when desired but also helps maintain an artificial gravityin the container.

A product gas delivery circuit is preferably provided, and includesconduit 65 branching from conduit 53. Branch conduit 65 containsvaporizer-superheater 66 which is preferably atmospherically heated, andgas regulator 67 at the discharge end of conduit 65. When product gasdelivery is required, regulator 67 is opened, lowering the pressure inconduit 65. Liquid then flows consecutively through lower end eductortube section orifices 57, eductor tube 64, conduit 58, three-way valve59, conduit 53, and hence into branch conduit 65. The liquid then passesthrough vaporizer-superheater 66 and the resulting warmed gas isdischarged through gas regulator 67 for use as desired. Expansion ofsprings 29 and 30 forces piston 23 to remain in contact with theremaining liquid and thus maintain the desired flow of liquid ratherthan gas from whatever position the container may lie. As previouslydiscussed, this feature is extremely advantageous for underwaterbreathing apparatus since divers must work in various positions. Thepresent invention also provides a continuous source of liquefied gas ofconstant composition to breathing systems for aircraft and space shipsunder inverted flight or zero-gravity conditions.

It is especially desired in underwater breathing apparatus that thediver have a reserve breathing supply to enable him to safely return tothe surface. In the apparatus of the present invention, lower eductortube orifices 57 may be located so that when piston 23 reaches a lowlevel covering these orifices and thus preventing further liquid flowtherethrough, the liquid remaining in inner vessel 11 below the orificesis equivalent to about five minutes breathing supply. After receivingthis warning, the diver may turn three-way valve 59 to permit flowthrough conduit 43 connected to the lower end of inner vessel 11. Thedownward movement of piston -23 under spring and gas phase pressure thenforces out the remaining emergency supply of liquid through bottomconduit 43, three-way valve 59, conduit 53, and the previously describedproduct gas supply system.

Fig. 2 illustrates an alternate modification of the lower portion of theimproved apparatus which is particularly appropriate when an emergencysupply of liquid is not required. Lower eductor tube orifices 157 arepositioned substantially at the bottom end of inner vessel 111, andconduit 158 is directly connected to liquid filling valve 141 andconduit 153. Vaporizers 154 and 166 serve the same purposes as doVaporizers 54 and 66, described above.

Fig. 3 illustrates a modification of the top portion of the novelapparatus in which the lower end of back-up spring 234 is positioned inthe annular circular recessed section 285 of spring retainer 233 and theupper end of such spring abuts the upper end of theinner vessel 211. Themost important advantage of this arrangement is a reduction in thediameter of hollow upper suspenmeta 10 sionmember 220. This feature inturn decreases the heat transfer toinner vessel 211 from the atmosphere,and consequently reduces evaporation of the stored liquid. Thisarrangement also permits a reduction in the overall height of thecontainer.

Figs. 4 and 5 illustrate still another embodiment of the invention inwhich the opacified insulation comprises low-conductive layers 390preferably formed offiber glass having fiber diameters of less thanabout 50 microns and radiation impervious layers 391 preferably formedof aluminum foil sheets having a thickness between about 0.2 millimeterand 0.002 millmeter. Such layers may be spirally wrapped around theinner vessel with one end of the insulation wrapping in contact with theinner vessel 311 and the other end nearest the outer casing 312.Alternatively, the layers may be mounted concentrically with respect tothe inner vessel 311. In either embodiment, the fibers of layer 390 arepreferably oriented substantially parallel to radiation imperviouslayers 391 and substantiallyperpendicular to the direction of heat flowacross the insulation space. The tightness and number of wrapping turnsmay be varied to suitthe insulating requirements of the particular container. Tightening of the insulation wrapping causes: the low conductiveand resilient fibrous material to be compressed into a smaller space.This action decreases: the percentage voids in the fibrous material, andincreases the cross-sectional area of the effective path of solidconduction. However, the voids are reduced in size, which results in theinsulation being less sensitiveto pressure changes in the vacuum space;On the other hand, wrapping the insulation too loosely decreases-thenumber of turns of radiation shielding in the insulation. space, andincreases heat leak by radiation. Optimum results are obtained somewherebetween these extremesv when the sum of the heat leaks due to radiationand conduction is a minimum. By providing a large number of turns ofinsulation wrappings, the passage or radiativeheat is substantiallyeliminated, while the con ducti've heat flow along the spiral path iseffectively reduced due to the lengthened heat path. A furtheradvantageous feature of the wrapped insulation embodi ment is that whenit completely fills the insulation space wall to wall, the insulationalso provides a good degree of support for the inner vessel,particularly against lateral accelerations.

It will be apparent from the foregoing description and the accompanyingdrawings that the preferred form of the present invention combines anumber of elements including a slidable piston, a flexible film forminga leak-tight seal around the piston, a longitudinal member with eductortube portions at each end, a pressure building circuit, aluminum oraluminum alloy construction, an opacified insulating jacket, and a gasadsorbent, in a manner so as to provide an improved portable containerfor carrying low-boiling liquefied gases. This container permitsdischarge of liquid therefrom when the container is in any position orunder any gravity condition, and has the characteristics of lighterweight, lower heat inleak and greater compactness and durability. I

Although preferred embodiments of the invention have been described indetail, it is contemplated that modifications of the apparatus may bemade and that some features may be employed without others, all 'withinthe spirit and scope of the invention.

What is claimed is:

l. A portable container for storing and dispensing from any containerposition, a pressurized liquefied gas having a boiling point below 233K., comprising an inner vessel for storing a body of said pressurizedliquefied gas; an outer shell enclosing and separating said inner vesselfrom the atmosphere to define an insulating space: under a vacuumpressure between said inner vessel and said outer shell; a pistontransversely positioned across s nses the cross-sectional area of theinner vessel so as to substantially fill such area, and being arrangedand constructed to slidably move in a direction parallel to thelongitudinal axis of such container so as to separatethe liquid and gasphases of said pressurized liquefied gas in said inner vessel; means forseparably and gas-tightly sealing said liquid phase from said gas phasewhile allowing substantially free sliding movement of said piston; meansfor maintaining said liquid phase under a slight artificial gravitypressure at all container positions and gravity conditions, said meanscomprising at least one compressible spring longitudinally positionedbetween the upper end of said inner vessel and the top side of saidslidable piston.

2. A portable container for storing and dispensing from any containerposition, a pressurized liquefied gas having a boiling point below 233K., comprising an inner vessel for storing a body of said pressurizedliquefied gas; an outer shell enclosing and separating said inner vesselfrom the atmosphere; an insulating space under a vacuum pressure betweensaid inner vessel and said outer shell; a piston transversely positionedacross the crosssectional area of the inner vessel so as tosubstantially fill such area, and being arranged and constructed toslidably move in a direction parallel to the longitudinal axis of suchcontainer so as to separate the liquid and gas phases of saidpressurized liquefied gas in said inner vessel; means for sealing theouter periphery of the slidable piston against the inner wall of saidinner vessel, including a concentrically positioned flexible cylindricalfilm having one end leak-tightly and circumferentially attachedto theinner wall of said inner vessel and the other end leak-tightly andcircum'ferentially attached to the outer periphery of said piston; meansfor maintaining said liquid phase under a slight artificial gravitypressure at all container positions and gravity conditions, said meanscomprising at least one compressible spring longitudinally positionedbetween the upper end of said inner vessel and the top side of saidslidable piston.

3'. A portable container according to claim 2 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K. in which said flexible cylindrical film issufficiently long in the longitudinal direction to transversely bendback on itself during movement of said slidable piston.

4. A portable container according to claim 1 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below about 233 K. in which said inner vessel and saidouter shell are constructed from a member of the group consisting ofaluminum and aluminum alloys.

5. A portable container according to claim l for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K. in which said piston is slidably mounted onan elongated member extending the longitudinal length of said innervessel, the upper portion of such member communicating with the gasphase of said pressurized liquefied gas as well as top gas conduitmeans, and the lower portion of said member communicating with theliquid phase of said pressurized liquefied gas as well as bottom liquidconduit means.

6. A portable container according to claim 1 for storing and dispensingfrom any container position, a. pressurized liquefied gas having aboiling point below 233 K. in. which said piston is slidably mounted onan elongated member extending the longitudinal length of said innervessel, the upper portion of such member cornmunicating with the gasphase of said pressurized liquefied gas as well as top gas conduitmeans, and the lower portion of said member communicating with theliquid phase of said pressurized liquefied gas as Well as bottom liquidconduit means; a pressure building circuit external to said outer shelland communicating at opposite ends with said bottom liquid conduit andtop gas conduit means, such circuit including a vaporizer for vaporizingthe liquid withdrawn through said bottom liquid conduit means, andpressure closing valve means for controlling the fluid flow throughsaidpressure building circuit.

7, A portable container according to claim 1 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K. in which said piston is slidably mounted onan elongated member extending the longitudinal length of said innervessel; such memberhaving a solid center section extending in thelongitudinal direction as well as upper and lower eductor tube endsections, the upper educto-r tube section communicating with the gasphase of said pressurized liquefied gas as well as top gas conduitmeans, and the lower eductor tube section communicating with the liquidphase of said pressurized liquefied gas as well as bottom liquid conduitmeans.

8. A portable container according to claim 6 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K. in which a product gas supply conduitcommunicates with said bottom liquid conduit means, said product gassupply conduit containing vaporizing and superheating means.

9. A portable container according to claim 1 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K. in which said piston is slidably mounted onan elongated member extending the longitudinal length of said innervessel, the upper portion of such member communicating with the gasphase of said pressurized liquefied gas; top gas conduit meanscommunicating with the upper end of said member; at least one orifice inthe lower portion of said member and positioned above the lower end ofsaid inner vessel for communication with the liquid phase of saidpressurized liquefied gas; first bottom liquid conduit meanscommunicating with the lower end of said member for liquid withdrawaltherethrough; second bottom liquid conduit means communieating with thelower end of said inner vessel for dlS- charge therethrough of at leastthe last portion of the stored liquid when said orifice in saidelongated member is sealed by the sliding piston.

10. A portable container according to claim 1 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K, in which means are provided for monitoringand visually indicating the liquid level of such liquefied gas body insaid inner vessel, such means comprising a retainer transverselyarranged and supported against the upper end of said compressible springto move in a longitudinal direction with the motion of such spring andsaid piston as actuated by the changing liquid level of said liquefiedgas body; a second compressible spring longitudinally alinged betweenthe top surface of said retainer and said upper end of said portablecontainer; a rod pointer having one end associated with the retainer topsurface for movement therewith and the other end longitudinallyextending into the upper end of said portable container, thelongitudinal movement of said pointer other end being observable as avisual indication of said liquid level.

11. In a double-walled vacuum insulated portable container for storingand dispensing from any container position, a pressurized liquefied gashaving a boiling point below 233 K. the improvement comprising a pistontransversely positioned across the cross-sectional area of the innervessel so as to substantially fill such area, and being arranged andconstructed to slidably move in a direc-. tion parallel to thelongitudinal axis of such container so as to separate the liquid and gasphases of said pressurized liquefied gas in said inner vessel; means forsealing the outer periphery of the slidable piston against the innerWall of said inner vessel, including a concentrically positionedflexible cylindrical film having one end leak-tightly andcircumferentially attached to the inner wall of said inner vessel andthe other end leak-tightly and circumferentially attached to the outerperiphery of said piston; means for maintaining said liquid phase undera slight artificial gravity pressure at all container altitudes andgravity conditions, said means comprising at least one compressiblespring transversely positioned across said inner vessel andlongitudinally located between the upper end of said inner vessel andthe top side of said slidable piston.

12. A method for supplying liquefied gas in any container position andunder any gravity condition from a double-walled vacuum insulatedportable container storing gas and liquid phases, comprising the stepsof providing in the inner vessel, a body of pressurized liquefied gashaving a boiling point below 233 K., applying a slight artificialgravity pressure to such liquid body so as to discharge liquid from thecontainer bottom, the artificial gravity pressure being applied by acontinuous force in addition to gas pressure acting on the entire liquidlevel surface of said liquid body, said force being applied in adirection parallel to the longitudinal axis of the container,maintaining separate the liquid and gas phases of the liquefied gas insaid inner vessel, and supplementing said force by gas pressure of vaporfrom said liquid body.

13. A portable container according to claim 1 for storing and dispensingfrom any container position, a pressurized liquefied gas having aboiling point below 233 K., in which said means for sealing the outerperiphery of the slidable piston against the inner wall of said innervessel comprises a flexible film.

14. A portable container according to claim 1 for storbetween the topsurface of said retainer and the upper end of said portable container; arod having one end associated with the retainer top surface for movementtherewith and the other end longitudinally extending into the upper endof said portable container and forming a contact with an electricalindicating circuit, the longitudinal movement of said rod other endactuating the electrical circuit and causing the remote indicatingdevice to register a change in liquid level.

References Cited in the file of this patent UNITED STATES PATENTS609,970 Lochmann Aug. 30, 1898 1,122,710 Feit Dec. 29, 1914 1,973,880Moody Sept. 18, 1934 2,396,459 Dana Mar. 12, 1946 2,604,230 Payne July22, 1952 2,657,542 Wildhack Nov. 3, 1953 2,861,715 Wissmiller et al Nov.25, 1958 2,900,800 Lcveday Aug. 25, 1959

